Bearing structure for sextants or the like



T. O. BRANDON BEARING STRUCTURE FOR SEXTANTS OR THE LIKE Filed Dec. 10, 1946 April 25, 1950 3 Sheets-Sheet l glwvwvtoo THOMAS O. BRANDON April 1950 Q T. o. BRANDON 2,504,960

BEARING STRUCTURE FOR SEXTANTS OR THE LIKE Filed Dec. 10, 1946 3 Sheets-Sheet 2 I8 2e 27 '4 low IO mg, '6 9 K 9 7 2 l5 l3 I Hm I m 28 3 ml 7. I

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F. IG 3 gwuwvboo THOMAS C. BRANDON April 25, 1950 l BRANDON 2,504,960

BEARING STRUCTURE FOR SEXTANTS OR THE LIKE Filed Dec. 10, 1946 SSheets-Sheet 3 F 5 THOMAS C. BRANDON Patented Apr. 25, 1950 i gg BEARING STRUCTURE FDR SEXTANTS OR THE LIKE Thomas 0. Brandon, United States Navy Application December 10, 1946, Serial No. 715,233

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 9 Claims.

The invention relates to a positive precision bearing structure, and relates more particularly to a positive precision bearing of an endless tangent screw sextant.

An object of the invention is the provision of a positive precision bearing which is capable of maintaining definite and constant bearing properties throughout its contact surfaces and which provides balanced stability in the bearing assembly.

Another object of the invention is to provide a sextant micrometer tangent screw and bearing structure which eliminates the back-lash caused by end play occurring in the types of sextant micrometer screw and hearing at present in use.

A further object of the invention is the provision of a bearing structure which is adapted to improve with use.

Other objects and advantages of the invention will be more apparent from the following description taken in connection with the accompanying drawings which are exemplary and in which:

Fig. l is a view of a portion of a sextant embodying the bearing and associated structure of the invention.

Fig. 2 is a View partly in section on line 2--2 of Fig. 1.

Fig. 3 is an external view of the bearing assembly of Figs. 1 and 2.

Fig. 4 is a view partly on line 4-4 of Fig. 1.

Fig. 5 is an enlarged fragmentary view partly in section showing the bearing surfaces and the relation between the rotary shaft and the bearing members.

Referring to the drawings, the numeral i represents the rotary shaft of the bear ng structure of the invention, here shown as embodied in a tangent screw assembly of a sextant, and in this embodiment the shaft 1 carries the tangent worm 2. A portion of the peripheryof the rotary shaft I is received in a bearing member 3 which is pivotally secured to the index arm 4 of the sextant by means of a screw 5. The screw 5 desirably overlies a bushing 24 received in an opening in the index arm 4. The bearing member or tangent arm 3 preferably carries a release finger 6 for actuation by the worm disengaging lever 1 against the action of the tangent spring 8 to rotate the "50 The bearing assembly about the pivot screw 5 to disengage the worm 2 from the sextant are 2!. tangent spring 8 is secured to the index arm i by means of a bracket member 25.

An outer or cap bearing member 9 receives and engages a portion of the periphery of the rotary in section substantially axis of the shaft.

shaft and is urged into engagement therewith by a bearing spring means H1 secured to the outer ends of screw posts or guide pin members Ii which are secured to the inner or pivoted bearing member or tangent arm 3 and extend through openings 12 in the outer or cap bearing member s. The bearing spring member IE! comprises a body portion extending longitudinally of said bearing and having spring ends Illa and Illb which engage the surface of the cap bearing member 9. Apertured ears extend from said bearing spring member and receive said pins and are retained by said pins. Desirably spring washer means 13 are disposed on said pins ll between the spring member Ill and the surface of the cap bearing 9. The outer bearing member or cap 9 is preferably provided with depending flange portions 29 which embrace a portion of the bearing member 3 as seen in Fig. 4.. The cap bearing member 9 is thus mounted for spring limited sliding movement relative to said pivoted bearing member 3 and against said rotary shaft l The tension on the spring means I!) and I3 is adjustable by means of the screw posts or pins I I.

- The rotary shaft I is provided with preferably a plurality of spaced apart annular enlarged portions preferably disposed one at each end of an inner cylindrical shaft portion of substantial length, the enlarged portions having oppositely facing inclined annular surfaces It and I5, and I6 and I1, respectively, and received in correspondingly shaped annular recesses formed in the bearing members 3 and 9. Desirably the surfaces may be, for example, at an angle 45 to the The shaft has cylindrical outer end portions extending beyond the inclined surfaces of said enlarged portions. According to the invention, the rotary shaft l and bearing members 3 and 9 are so constructed that the only engagement between the rotary shaft and the bearing members is at the inclined surfaces i4, i5, i8 and il. Clearance or spacing is elsewhere provided between the adjacent surfaces of the rotary shaft and bearing members, as indicated at the cylindrical portions, and also provides space for lubricating grease. The said annular recesses formed in the bearing members may desirably include a central groove 22, spacing the bearing members from a flattened apexportion 23 preferably provided on the shaft l. Desirably the central or inner cylindrical portion of the rotary shaft may be of reduced diameter in re spect to the cylindrical outer end portions thereof as "seen in Fig. 2, which provides increased inclined bearing surfaces is and it. The spring known types of sextant micrometer screw bearings.

The worm disengaging lever 1 engages a fixed 7 arm or lever 213 which is employed in the usual manner in operating the lever 1, to disengage the worm.

It will be observed that the shaft l is provided with a terminal hub 26 and a flange 21. The hub receives the micrometer drum '18 which abuts the flange 23' and is secured to the hubby means of screw 28. The shaft also receives a vernier member "19 embracing "the shaft and interposed 'between theiflang'e .2?! and the bearing or tangent arm dandpverlying the end thereof and overlying the end of the outer or cap bearing member. The Vernier is suitably secured to the bearing member 3*a's :by means of :screw means 28', According 'to the invention, the hub 26 :is milled. to provide fifl'teeth'to fit corresponding V-shaped teeth provided in the drum bore. This provides .for accurate adjustment :to the minute in collimating the device. :An adjustment :of one or more teeth correspondingto :one :or: more minutes, can be :made by "withdrawing the drurn'unti-l the teeth are disconnected :and rotating zit-a "distance of one or more teeth, and "then replacing it *with the teeth connected in the newly adjusted position;

The inter-connected teeth provide :.a positive anti-slip connection "between the :drum and the hub irrespective of whether ior not 'the screw '28 is fully tight, so that :any possibility :of mis-adjustment is-substantially eliminated. The drum is also provided with 160:indicia zdivisi'ons spaced around its periphery. Also for use in collimation, the screw holes in the Vernier may be slightly larger than the screws'to allow for some adjustment of the vernier in respectto the bearing and drum.

The entireassembly :is capable-of-being readily assembled and disassembled, :as will be readily apparent from the structure as described, and provides a rugged and 510mg wearing assembly capable "of maintaining absolute accuracy indefinitely.

While butone embodiment of the invention has been shown and described, it will 'be understood that the invention is not -to be limited thereto and that numerous changes and-modifications may be made therein without departing from the spirit and scope of the invention which is only to be limited by the terms of the appended :claims.

The invention described herein maybe manufactured and used by or for the Government :of the United States of America for governmental purposes without'the "payment "of any royalties thereon or therefor.

What-is claimedisz 1. In a =bear'ingstructuraa rotary shaftrmemher, a bearing member secured to tasupportiand receiving a peripheral portion of therotary-shsft, a cap bearing member engaging a peripheral portien of the shaft and overlying the-shaft and said secured bearing member, means connecting said bearing members comprising :gu-ide pin ymeans secured to said secured bearing and --extending through said cap bearing to permit slidable movement of said cap bearing on said pins relative to said secured bearing, and spring means secured to the outer ends of said pins and yieldably engaging said cap bearing to ur e said cap bearing against the rotary shaft, said rotary shaft havin an inner. cylindrical portion of substantial length, and a plurality of spaced apart annular enlarged portions, one adjoining each end of said inner cylindrical shaft portion, and outer cylindrical shaft portions one adjoining the outer side of each of said annular enlarged portions, said spaced annular enlarged portions of said shaft each having oppositely facing annular inclined bearing surfaces, and said bearing members having correspondingly shaped bearing recesses to receive said oppositely facing inclined bearing surfaces :of the annular enlargements of the rotary shaft-said inclined cooperating bearing surfaces of said plurality of annular enlarge- ,ments and :of saidrbearing recesses being of such =ecliinensional extent as to provide definite spacing ofthe inner and outer cylindrical portions of the rotary shaft from said ibearing members, tsaid spring means comprising a bearing spring member having a body portion extending longitudinally of :said bearing and overlying said cap bearing member and :havingspring ends engaging said cap bearing member at .points overlying said spaced annular enlarged portions of said rotary :shaf-t, said bearing spring member having aperture-d ears extending:l-aterallyifromsaid body portion andvreceiving and being retained by said :spin means, :said structure providing balanced V stability in the bearing assembly.

,2. In:a--bearin;g:structure 'accordingto claim 1,- .rspring washer ,means disposed "between said cap bearing member and the said earsfofssaidbearing zspring :member.

T3. In asbearing structure a rota-ryrshaft mem- -ber,;a bearing :mem'ber secured to a support and receivingsa pieripheralportionof the rotary shaft, a cap bearing member engaging :a peripheral por- ?tion-of-:t-he :sha-ft:and overlying; the. shaft and said secured bearing member, means connecting said bearing members comprising guide pin means secured to said secured bearing and extending throughsaidicap' bearing toper-m-it sl-idable move ment of said cap bearing :onsaid pins relative to said secured bearing, and spring means secured to the outer ends of said pinsand yieldably engaging said cap-bearing to urge said cap'bearing f-against the rotary shaftgsaid rotary shaft having an inner cylindrical'portion-of substantial length, and a plurality of spaced apart annular enlarged port-ions, one adjoining each end of said inner icylindrica-l shaft portion, and outer cylindrical shaft portionsone adjoining the outer side of :each of said annular enlarged portions, said spaced annular enlarged'portions of said shaft each having oppositely facing annular inclined bearing surfaces, and said bearing members hav- :ing correspondinglyshaped bearing recesses to receive said oppositely facing inclined bearing surfaces of "the annular .lenlargements of the rotary :shaft, said inclined cooperating bearing :surfaces 40f :said plurality of annular enlarge- :mentsamdof isaid bearing recesses being of such rdimensionalxextentas toprovide definite spacing nf-the said inner and outer cylindrical portions of :therotaryshaft from said bearing members, said inner cylindrical portion of said shaft between said annularlenlargementsbeing of smaller diameter than ,thelsaidrouter cylindrical portions at the outer sideuof said annular enlargements,

the inner inclined bearing surfaces of said annular enlargements, which adjoin the smaller diameter. inner cylindrical shaft portion, being of greater extent and bearing surface than the outer inclined bearing surfaces of said annular enlargements which adjoin the outer cylindrical portions at the outer sides of said enlargements, said structure providing balanced stability in the bearing assembly.

4. In a bearing structure, a rotary shaft member, a bearing member secured to a support and receiving a peripheral portion of the rotary shaft, a cap bearing member engaging a peripheral portion of the shaft and overlying the shaft and said secured bearing member, means connecting said bearing members comprising guide pin means secured to said secured bearing and extending through said cap bearing to permit slidable movement of said cap bearing on said pins relative to said secured bearing, and spring means secured to the outer ends of said pins and yieldably engaging said cap bearing to urge said cap bearing against the rotary shaft, said rotary shaft having an inner cylindrical portion of substantial length, and a plurality of spaced apart annular enlarged portions rigid with said shaft, one adjoining each end of said inner cylindrical shaft portion, said rigid spaced apart annular enlarged portions of said shaft each having oppositely facing annular inclined bearing surfaces and said bearing members having correspondingly shaped spaced apart bearing recesses to receive said oppositely facing inclined bearing surfaces of the spaced apart annular enlargements of the rotary shaft, said inlined cooperating bearing surfaces of said plurality of spaced apart annular enlargements and of said corresponding bearing recesses being of such relative dimensional extent as to provide definite spacing of the said cylindrical portion of the rotary shaft from said bearing members, said structure providing balanced stability and positive precision in the bearing assembly.

5. In a bearing structure according to claim 4, said spring means being unitary and having portions secured to the outer ends of said pins and having portions overlying and yieldably engaging said cap bearing at spaced locations thereon.

6. In a bearing structure according to claim 4, said cap bearing member having depending portions embracing and guided on said secured bearing member.

7. In a tangent arm micrometer screw structure for a sextant, with a rotary shaft carrying a tangent Worm at one end and a micrometer drum structure at the other end thereof, an inner elongated bearing member secured to the index arm of the sextant and being recessed throughout its length and receiving a portion of the periphery of said rotary shaft, an elongated outer cap bearing member recessed throughout its length and complementary to said inner bearing member and receiving a portion of the periphery of said shaft, the ends of said inner and outer complementary elongated bearing members being embraced in close proximity by the drum structure and worm, said drum structure and warm being of larger diameter than said shaft and substantially overlying the respective ends of said complementary bearing members, said inner bearing member being pivotally attached to said index arm and having a release finger thereon, screw pin means threadedly received in said pivoted inner bearing member and passing through said outer cap bearing member to permit slidable movement of said outer cap bearing member relative to said pivoted inner bearing member, spring means secured to the outer ends of said pin means and engaging the cap bearing memberto urge it against the rotary shaft, said screw pin means being adjustable to adjust the tension on said spring means, said rotary shaft having an inner cylindrical portion of substantial length, and a plurality of spaced apart annular enlarged portions one adjoining each end of said inner cylindrical shaft portion, and outer cylindrical shaft portions one adjoining the outer side of each of said annular enlarged portions, said spaced annular enlarged portions of said shaft each having oppositely facing annular inclined bearing surfaces, and said bearing members having correspondingly shaped bearing recesses to receive said oppositely facing inclined bearing surfaces of the annular enlargements of the rotary shaft, said inclined cooperating bearing surfaces of said plurality of annular enlargements and of said bearing recesses being of such dimensional extent as to provide definite spacing of the said inner and outer cylindrical portions of the rotary shaft from said bearing members.

8. In a tangent arm micrometer screw structure for a sextant, with a rotary shaft carrying a tangent worm at one end and a micrometer drum structure at the other end thereof, an inner elongated bearing member secured to the index arm of the sextant and being recessed throughout its length and receiving a portion of the periphery of said rotary shaft, an elongated outer cap bearing member recessed throughout its length and complementary to said inner bearing member and receiving a portion of the periphery of said shaft, the ends of said inner and outer complementary elongated bearing members being embraced in close proximity by the drum structure and worm, said drum structure and worm being of larger diameter than said shaft and substantially overlying the respective ends of said complementary bearing members, said inner bearing member being pivotally attached to said index arm and having a release finger thereon, screw pin means threadedly received in said pivoted inner bearing member and passing through said outer cap bearing member to permit slidable movement of said outer cap bearing member relative to said pivoted inner bearing member, spring means secured to the outer ends of said pin means and engaging the cap bearing member to urge it against the rotary shaft, said screw pin means being adjustable to adjust the tension on said spring means, said rotary shaft having an inner cylindrical portion of substantial length, and a plurality of spaced apart annular enlarged portions one adjoining each end of said inner cylindrical shaft portion, and outer cylindrical shaft portions one adjoining the outer side of each of said annular enlarged portions, said spaced annular enlarged portions of said shaft each having oppositely facing annular inclined bearing surfaces, and said bearing members having correspondingly shaped bearing recesses to receive said oppositely facing inclined bearing surfaces of the annular enlargements of the rotary shaft, said inclined cooperating bearing surfaces of said plurality of annular enlargements and of said bearing recesses being of such dimensional extent as to provide definite spacing of the said inner and outer cylindrical portions of the rotary shaft from said bearing members, a vernier member embracing said shaft and disposed between said drum and the bearing members and overlying the proximate end of 

